Injectors and ECMs

[Richard Wakeling]

Hi Ron,
Ron Gregory wrote:
> 
> I have a buddy that has gone completely overboard with
> his Syclone.  We are now running out of injector.  He
> wants to go with huge injectors.  He also wants to go with
> the new Felpro SEFILO8 ECM, because the guy that sold
> him his camshaft said the stock ECM wouldn't work....
> I want to prove him wrong by using the stock ECM and
> maybe he'll give me some of the $2400 for helping....
> 
> We are working on a GMC Syclone... using the
> Delco 1227749 ECM.  This is the same ECM that was
> used on the '87-90 turbo 2.0 'M' cars [Sunbird].  This
> ECM has two injector drivers, but from what I've
> already learned, it only uses one injector driver.

This is what I believe to be correct.

> So, does that mean that all six injectors are fired at once,

Yes all injectors fire at the same time. Saturation method

> or does that one driver fire for each bank????
> 
> Does anyone know if the turbo S-bird only used one driver, too?
> Or did it use both...

The Sunbird turbo uses two drivers. Two injectors on each driver using
peek and hold method.

 and had different wiring... some pins the Sy
> doesn't use...

Yes the Sunbird turbo used c10 and c11 as injector outputs.
Whereas the Syclone used c11 and c12 which are joined inside the ECM.

On the Sunbird:
c13 and c15 were jumpered to add a .1 ohm resistor to the source and to
ground for one of the injector drivers to operate in peek and hold.

d5 and d6 were also jumpered to add another .1 ohm resistor to the
source and ground for the second injector driver again to operate in
peek and hold.
> 
> My buddy just bought a set of six 55 lb/hr Seimans low-ohm
> fuel injectors [cheaper than a set of MSD high-ohm injectors]...
> yes... *before* I got all the answers... as usual...
> Someone [a turbo Regal expert] told him that all he had to
> do was swap-out the injector drivers.... maybe for a GN, but
> I doubt a Syclone... noone listens to me...
> 
> Are low-ohm drivers intended to drive only one injector?

This would probably be the ideal situation.

> Is it true that the low-ohm injectors are more stable... flow more
> predictably?

In my experence low-ohm injectors which are usualy driven peek and hold
are more stable at small pulse widths so idle is usually more stable
with larger injectors with low z injectors driven peek and hold.
   
> Would it be worth the effort to build a small interface board to
> drive those low-ohm injectors via the current driver on the
> ECM? 

This is one option.

 What would that buy us?
> 
> Would putting that 10-ohm resistor on each low-ohm injector

This does work but it is not as good as running them peek and hold.
If you don't use the 10-ohm resistor the injectors and drivers will
overheat and probably give you an intermitant code 42.
The problem using the 10-ohm resistor is you are not getting the full
and correct drive across the injector.

> buy us anything other than the ability to use the injectors that
> he already bought... if that?
> 
> I don't have [any of] the answers... please help...
> [pick all tha apply]
> 
> *  get high-ohm injectors, 'cause they aren't bad
> *  go with Felpro ECM and low-ohm injectors
> *  build a board to drive low-ohm injectors with
>    GM ECM..
> *  check caller-ID box and don't answer the phone
>    any more when that clown calls back

There maybe a possibily that you could drive three injectors peek and
hold from each of the drivers. Don't forget the Sunbird is driving two.
The injector loom would have to be modified so you had two seperate
circuits. The injector wiring then would have to be the same as the
Sunbird turbo ( with jumpers) so the only other question is will both
drivers get the nescessary signals from the Syclone software.

Cheers Richard.
sorry about the spelling.
 
> Thanks,
> ~~~~~~
> Ron Gregory                 Syclone VIN #1452
> rgregory at iname.com          Garland, TX